This invention relates to the desulfurization and liquefaction of coal. More specifically, this invention relates to a catalytic process for the desulfurization and liquefaction of coal which uses inexpensive synthesis gas.
Recent petroleum and natural gas shortages and environmental problems underline the great importance of developing alternative sources of clean energy in this country. While vast resources of coal are available, it is not as attractive as a source of energy because of its physical and chemical properties. Because coal is a solid which contains considerable ash, it is inconvenient and expensive to transport and utilize. Furthermore, much of the coal available contains relatively high concentrations of sulfur which, upon combustion, is released to the atmosphere as a pollutant unless recovered by expensive equipment before dispersal.
Considerable effort is now being expended to develop processes to desulfurize and liquefy the coal to form a carbonaceous liquid product which can either be used as a fuel oil or processed further to produce additional petroleum products. One such process for the desulfurization and liquefaction of coal is described in U.S. Pat. No. 3,840,456. However, this process and similar processes either require or prefer that carbon-monoxide-free gas be used with the process to obtain desirable results. However, hydrogen which is free of carbon monoxide is expensive and in short supply, since it is generally produced by the reaction of steam with a hydrocarbon source such as natural gas or coal to produce a synthesis gas. The synthesis gas as produced is an admixture of carbon monoxide, some carbon dioxide and hydrogen. This "raw" synthesis gas is then passed through a shift converter to produce the carbon dioxide and additional hydrogen. Since the gas still contains about 3% residual carbon monoxide, further processing will be required before the gas can be used with a carbon-monoxide-sensitive catalyst.